Modulated quasi-resonant peak-current-mode control

Abstract

Driver circuitry is configured to generate a control signal for a switching device that controls supply of load current to a load. The driver circuitry includes current control circuitry, modulation circuitry, and signal generation circuitry. The current control circuitry is configured to generate a current signal indicative of whether the load current has reached a reference current. The modulation circuitry is configured to generate a modulation signal having an ON-time that is based at least on a desired amount of current to be supplied to the load. The signal generation circuitry is configured to generate the control signal based at least on the current signal and the modulation signal.

What is claimed is: 
     
       1. Driver circuitry configured to generate a control signal for a switching device that controls supply of load current to a load, the driver circuitry comprising:
 zero crossing detection circuitry configured to generate a valley detection signal when the load current crosses zero; 
 current control circuitry configured to generate a current signal indicative of whether the load current has reached a reference current; 
 modulation circuitry configured to generate a modulation signal having an ON-time that is based at least on a desired amount of current to be supplied to the load; 
 signal generation circuitry configured to generate the control signal including a pulse that causes the switching device to operate an ON state in which current is supplied to the load by: 
 generating a rising edge of the pulse when i) the modulation signal is high and ii) a valley detection signal is received; and 
 generating a falling edge of the pulse when the current signal indicates that the load current has reached the reference current. 
 
     
     
       2. The driver circuitry of  claim 1 , wherein the signal generation circuitry is configured to:
 generate
 the rising edge of the pulse when i) the modulation signal is high and ii) a first valley detection signal is received. 
 
 
     
     
       3. The driver circuitry of  claim 1 , wherein the current control circuitry comprises reference current control circuitry configured to determine the reference current based at least on an operating parameter of the load. 
     
     
       4. The driver circuitry of  claim 3 , wherein the operation parameter comprises a temperature of the load. 
     
     
       5. The driver circuitry of  claim 3 , wherein the load comprises a light emitting diode and the operating parameter comprises a brightness produced by the light emitting diode at the reference current. 
     
     
       6. The driver circuitry of  claim 1 , wherein the modulation circuitry is configured to generate the modulation signal having no less than a minimum frequency. 
     
     
       7. The driver circuitry of  claim 6 , wherein the modulation circuitry is configured to, when the desired amount of current is less than the current that is supplied to the load to produce a modulation signal having the minimum frequency, generate the falling edge of the pulse prior to the when the current signal indicates that the load current has reached the reference current. 
     
     
       8. The driver circuitry of  claim 1 , wherein the modulation signal comprises a pulse-density-modulation (PDM) signal in which a ratio of high pulses to low pulses in the control signal within a pulse period controls the amount of current to be supplied to the load. 
     
     
       9. The driver circuitry of  claim 1 , wherein the modulation signal comprises a pulse-width-modulation (PWM) signal in which a width of a pulse in the control signal relative to a pulse period controls the amount of current to be supplied to the load. 
     
     
       10. The driver circuitry of  claim 1 , wherein the modulation signal comprises a pulse-frequency-modulation (PFM) signal in which a frequency of pulses in the control signal controls the amount of current to be supplied to the load. 
     
     
       11. A method, comprising:
 receiving a current signal indicative of whether load current flowing through a load has reached a reference current; 
 receiving a valley detection signal indicating that the load current crosses zero; 
 generating a modulation signal having an ON-time that is based at least on a desired amount of current to be supplied to the load; and 
 generating a control signal for a switching device that controls supply of current to the load, wherein the control signal includes a pulse to cause the switching device to operate an ON state in which current is supplied to the load, wherein generating the control signal includes:
 generating a rising edge of the pulse when i) the modulation signal is high and ii) a valley detection signal is received; and 
 generating a falling edge of the pulse when the current signal indicates that the load current has reached the reference current. 
 
 
     
     
       12. The method of  claim 11 , further comprising:
 generating the rising edge of the pulse when i) the modulation signal is high and ii) a first valley detection signal is received. 
 
     
     
       13. The method of  claim 11 , further comprising determining a value for the reference current based at least on an operating parameter of the load. 
     
     
       14. The method of  claim 13 , wherein the operation parameter comprises a temperature of the load. 
     
     
       15. The method of  claim 13 , wherein the load comprises a light emitting diode and the operating parameter comprises a brightness produced by the light emitting diode at the reference current. 
     
     
       16. The method of  claim 11 , further comprising generating the modulation signal having no less than a minimum frequency. 
     
     
       17. The method of  claim 16 , further comprising, when the desired amount of current is less than the current that is supplied to the load to produce a modulation signal having the minimum frequency:
 generating the falling edge of the pulse prior to the when the current signal indicates that the load current has reached the reference current. 
 
     
     
       18. Driver circuitry configured to generate a control signal for a switching device that controls supply of load current to a load, the driver circuitry comprising:
 comparator circuitry configured to generate a current signal indicative of whether the load current has reached a reference current; 
 brightness color control unit circuitry (BCCU) configured to generate a modulation signal having an ON-time that is based at least on a desired amount of current to be supplied to the load; 
 capture and control unit circuitry (CCU) configured to generate the control signal based at least on the current signal and the modulation signal, wherein the CCU comprises a counter configured to:
 generate a rising edge of the control signal in response to counting a certain number of increments after a zero crossing of the load current is detected; and 
 generate a falling edge of the control signal in response to a falling edge of the CCU signal. 
 
 
     
     
       19. The driver circuitry of  claim 18 , wherein the CCU is configured to generate a falling edge of the control signal upon expiration of a predetermined number of counts since a last FLUSH input that clears the CCU counter.